We use following methods to insert, delete and retrieve elements in
a HashMap.
1. Retrieve: We use get() method to retrieve elements from a
HashMap.
Value get(Object key)
2. Insert: We use put() method to insert a key value pair in a
HashMap.
Value put(Key k, Value v)
3. Delete: We use remove() method to delete key-value pair
from the HashMap.
Value remove(Object key)